General aviation aircraft and large commercial jets are vulnerable to lightning strike. Unlike their metal counterparts, composite structures in these aircraft do not readily conduct away the extreme electrical currents and electromagnetic forces generated by lightning strikes.
Aircraft with composite structures may be equipped with lightning strike protection (LSP). For example, conductive media may be provided on a surface or in a structure to divert and distribute lightning current.
A problem exists with determining whether lightning current has traveled through a particular region of an aircraft. A lightning strike might attach and detach at separate locations, and the lightning current might follow LSP paths or unpredictable paths therebetween. As but one example, lightning might attach at the nose of the fuselage, follow paths toward the aft of the fuselage, and detach at a random location on a horizontal stabilizer. Damage to composite material can occur at the locations of lightning attachment and detachment. Damage to composite material can also occur along paths taken by the lightning current.
The damage caused by a lightning strike might be hidden, or it might not be apparent through visual inspection. To detect damage caused by a lightning strike, very large areas of an aircraft structure might have to be examined. However, non-destructive inspection (NDI) on very large areas is time-consuming and expensive. Moreover, specific areas (e.g., areas containing surface pitting and paint damage) can be missed if a very large area has to be inspected.